Anatomical considerations for the injection of botulinum neurotoxin in lower extremity contouring: a cadaveric study

Abstract

BackgroundBotulinum neurotoxin (BoNT) is increasingly used for aesthetic contouring of the lower extremities, particularly for reducing calf muscle hypertrophy to achieve a slimmer leg silhouette. However, successful outcomes require precise anatomical knowledge of target muscles and their intramuscular neural distribution.This study aims to define optimal BoNT injection zones for key lower limb muscles based on detailed anatomical mapping, to guide safe and effective lower extremity contouring.BackgroundBotulinum neurotoxin (BoNT) is increasingly used for aesthetic contouring of the lower extremities, particularly for reducing calf muscle hypertrophy to achieve a slimmer leg silhouette. However, successful outcomes require precise anatomical knowledge of target muscles and their intramuscular neural distribution.This study aims to define optimal BoNT injection zones for key lower limb muscles based on detailed anatomical mapping, to guide safe and effective lower extremity contouring.MethodsA total of 48 muscles-including the gastrocnemius, soleus, peroneus longus, peroneus brevis, vastus medialis, and vastus lateralis-were dissected from Korean cadavers. Intramuscular neural arborization patterns were identified using a modified Sihler's staining technique. Each muscle was divided into standardized zones to determine ideal injection sites based on nerve distribution and bulk.ResultsFor the soleus, optimal injection sites were identified in Zones 3 and 5; for the gastrocnemius, Zones 3-4 showed the highest nerve arborization. The peroneal muscles and vastus group also showed region-specific neural patterns that guided targeted injections. Recommended dosing strategies were proposed to reduce hypertrophy while preserving muscle function. Ultrasound guidance was emphasized for deep or structurally sensitive muscles.ConclusionsZone-based BoNT injection techniques informed by neural mapping offer a safer and more effective approach to lower extremity contouring. These anatomical insights can optimize aesthetic outcomes and minimize functional complications. Further clinical studies are needed to validate long-term efficacy and refine dosing protocols.Level of Evidence: Not ratable.ConclusionsZone-based BoNT injection techniques informed by neural mapping offer a safer and more effective approach to lower extremity contouring. These anatomical insights can optimize aesthetic outcomes and minimize functional complications. Further clinical studies are needed to validate long-term efficacy and refine dosing protocols.Level of Evidence: Not ratable.